An image display apparatus having a display panel such as a liquid crystal panel or the like is provided in the market. This liquid crystal panel is a flat panel display that is thin, lightweight and low power consumption. The liquid crystal panel has a display area arranged in a central portion of the panel in which an image is displayed, a frame area which is arranged in an area surrounding the display area, and a terminal area which is arranged in an area surrounding the frame area. A plurality of scanning lines and data lines which are perpendicular to each other are arranged in the display area. Each scanning lines are regular intervals with each other and are arranged in parallel, and each data lines are regular intervals with each other and are arranged in parallel. One pixel is formed in a minimum area surrounded by the scanning line and the data line. A plurality of external connection terminals which are connected to output pins (output terminals) of a driving circuit that outputs a control signal are formed in the terminal area. A plurality of interconnection lines for connecting the scanning line and the data line with the external connection terminal are formed in the frame area.
The control signal from the output pins of the driving circuit is transmitted through the external connection terminal, the scanning line and the data line, and applied to a pixel. Because the transmittance of the pixel is controlled by this control signal, an image display apparatus can perform the image display. In the following description, the scanning line and the data line are described generically as a signal line, and the distance between adjacent signal lines is described as a signal line pitch. One group of external connection terminals that correspond to the number of output pins of the driving circuit is described as a terminal block. Accordingly, the plurality of external connection terminals are divided into many terminal blocks. The spacing between the adjacent external connection terminals in the terminal block is described as a terminal pitch.
Generally, because the signal line pitch is greater than the terminal pitch, the signal line is connected to the external connection terminal with the interconnection line by performing a pitch adjustment of the signal line pitch and the terminal pitch. Because the length of the interconnection line differs depending on locations at which the external connection terminal and the signal line are arranged, the resistance value of each interconnection line differs depending on the locations at which the external connection terminal and the signal line are arranged. When the resistance value of the interconnection line is large, signal degradation of the control signal transmitted from the external connection terminal to the pixel becomes large. The signal degradation causes image quality degradation of a displayed image.
By the way, the length of each interconnection line connected in the one terminal block does not change rapidly, but changes gradually. Because the resistance value difference between the adjacent interconnection lines is small, image quality difference between the adjacent interconnection lines become small. Therefore the image quality degradation is invisible.
However, the length of the interconnection line in one terminal block largely differs from the length of the interconnection line in another terminal block. Especially, the length of the interconnection line located at the end of one terminal block largely differs from the length of the interconnection line that is adjacent to the above interconnection line in the one terminal block and located at the end of another adjacent terminal block. When the length difference between the adjacent interconnection lines is large, the resistance difference between the adjacent interconnection lines is large and the image quality difference between them becomes large. Accordingly, the image quality degradation becomes visible.
Accordingly, a technology with which the image quality degradation is suppressed by making the resistance values of the interconnection line equal to each other has been developed. For example, a technology with which the resistance values of the interconnection line are made equal to each other by forming the interconnection line in a meandering shape and differentiating the widths of the interconnection line from each other is proposed in Japanese Patent Application Laid-Open No. 1998-153791 and Japanese Patent Application Laid-Open No. 2003-140181.
When the resistance values of the interconnection line are made equal to each other by forming the interconnection line in a meandering shape and differentiating the widths of the interconnection line from each other, a space in which the interconnection line is formed in the meandering shape and the widths of the interconnection line are differentiated from each other is necessary. Additionally, when the width of the interconnection line is expanded, a space in which the width of the interconnection line is expanded while preventing a short circuit between the interconnection lines is necessary.
It has been required to develop a display panel whose image display density is high and whose frame area is small for an image display apparatus. However, it is difficult to secure the above-mentioned space while satisfying these requirements. Therefore, it has been difficult to produce an image display apparatus having high image quality because the resistance values of the interconnection line cannot be made sufficiently equal to each other.